Nitrileurea urethane elastomers with a structure modified by an amide derivative
Polimery 1996, No 6, 350
A new type of nitrileurethane (PNMU) elastomers, namely polynitrileurea urethaneamides(PNMUA), has been prepared by modifying the structure of PNMU elastomers with the product of reaction in a 2:1 molar ratio of dicyandiamide (DCDA) with adipic acid (KA). KA causes an effective breaking-up of DCDA crystals during conventional dehydration of one of the reactants — oligo(ethylene adipate)(OAE). The typical second reactant in the synthesis of PNMUA is diphenylmethane4,4'-diisocyanate. Besides DCDA, the product of the reaction of DCDA with KA is an additional chain extender which is very reactive towards isocyanate groups and modifies the structure of PNMU to the desired extent. An advantageous range of OAEs acid number values has been established, promoting an efficient break-up of very large DCDA crystals with the basic features of the structure and macroscopic properties remaining almost unaffected at the level characteristic for the unmodified PNMU elastomers. The modification affects only slightly the structure (mole ratio of soft to rigid segments) and the mechanical properties in comparison to typical urethane elastomers. The results illustrate an efficient chemical-aided process of breaking-up crystals of a solid reactant to enhance its reactivity.
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